bug#8876: 24.0.50; making `menu-bar-update-buffers' use another frame

[Stefan Monnier]

> Dunno what the problem was with using `last-command-event', which caused
> you to switch to the lambda code above.

Somehow I do remember why: using buffers as events is not really
supported and was leading to some bugs (which I can't remember) in some
corner cases.  So I changed the code to use more normal events (numbers)
and embed the buffer in the command itself (as a closure, basically)
which is conceptually much cleaner.

> It was so simple and flexible before; it seems so complex and monolithic
> now.
 
Feel free to change it so that instead of calling `switch-to-buffer' it
calls some alias or it (funcall menu-bar-select-buffer-function <buf>).


        Stefan